1. Field of the Invention
This invention relates generally to motor drive systems and, more particularly, to motor drive systems that operate bidirectionally to convert and control power from a secondary battery or other bidirectional dc source to mechanical power and also to bidirectionally convert and control external ac power to dc power for battery recharging and discharging.
2. Description of the Related Art
Both the motor and power processing systems used in electrically powered vehicles have demanding requirements; cost, weight, and energy conversion efficiency are each critical. In addition, the motor power processor (termed the drive system) must be capable of efficiently handling large ranges of speed and torque for both motoring and regeneration; low torque-response times and high operational reliability are also crucial. Besides the drive system function, a recharge function is also required wherein ac line power is converted to dc power for battery recharge. The requirements of cost, weight, and energy efficiency are also critical for the recharge function. Furthermore, high power factor, low EMI, and flexibility with respect to line voltage and line frequency are also crucial.